It was necessary to blend in an organic ultraviolet absorbent and such to give sunscreen cosmetics a high SPF value. For the organic ultraviolet absorbent to be blended into the ultraviolet absorbent, there are oil soluble ultraviolet absorbents and water soluble ultraviolet absorbents. The water soluble ultraviolet absorbents had a problem in that, compared with the oil soluble ultraviolet absorbents, they were less likely to fully achieve the expected SPF function. Therefore, the oil soluble ultraviolet absorbents are often blended into sunscreen cosmetics and, even when water soluble ultraviolet absorbents are blended in, generally the oil soluble ultraviolet absorbents are also blended in.
On the other hand, sunscreen cosmetics are particularly desired to give a freshing texture upon use. However, when the oil soluble ultraviolet absorbents are blended in, compared with the water soluble ultraviolet absorbents, the sunscreen cosmetic's tactile sensation upon use becomes oily and the important freshing texture is lost.
When blending an oil soluble ultraviolet absorbent into a sunscreen cosmetic, it is common to adopt a formulation form of emulsion such as an oil-in-water emulsified composition or a water-in-oil emulsified composition. That is, if an oil soluble ultraviolet absorbent is to be blended in, the formulation form is limited to an emulsion.
Also, Patent Document 1 reports that, as technology for securing the tactile sensation upon use and the stability of a sunscreen cosmetic, and particularly for sunscreen cosmetics made of an oil-in-water emulsified composition, a thickener obtained by microgelation of a hydrophilic compound having a high gelating ability, such as agar, contributes highly to the usability and stability of the cosmetic.
And, as reported in Patent Documents 2-4, a technology is known in which, for oil-in-water emulsified composition sunscreen cosmetics having fine particles of an ultraviolet scattering agent such as titanium oxide and zinc oxide dispersed in the inner oil phase, a common thickener such as succinoglucane, xanthan gum, and acrylamide is blended in to thicken the system and stably disperse not only the emulsified particles but the fine particles into the water phase.
Patent Document 5 provides an oil-in-water emulsified sunscreen cosmetic that does not have a high blend ratio of an oil soluble ultraviolet absorbent, achieves both the ultraviolet protection effect and stability without sacrificing a freshing texture upon use, and provides superior uniformity of the coating film and usability (absorption into the skin). Although Patent Document 5 has a one-line description of agar as the thickener for the potential ingredients, it has no description of the augmentation of the ultraviolet absorption effect of a water soluble ultraviolet absorbent by means of an agar microgel as achieved by the present invention. Furthermore, the invention of Patent Document 5 also contains an oil soluble ultraviolet absorbent.
Also, Patent Document 6 discloses an oil-in-water emulsified composition sunscreen cosmetic that contains both phenylbenzimidazole sulfonic acid, as a water soluble ultraviolet absorbent, and an oil soluble ultraviolet absorbent together. However, similarly to Patent Document 5, there is no description or suggestion of the unpredictable effect of increasing the ultraviolet absorption of the water soluble ultraviolet absorbent by means of an agar microgel as achieved in the present invention. Also, this document does not describe any extreme restriction of the blend ratio of the oil soluble ultraviolet absorbent or not blending in thereof.